An experiment was conducted to study the effects of nano titanium dioxide on essential oil yield and other traits of cumin (Cuminum cyminum L.). Factorial experiment based on a complete randomized block design with four replications was done, in the years of 2013 and 2014, in Garmsar- Iran. Treatments of various concentrations of titanium dioxide nanoparticle (0, 0.02%, 0.04% and 0.06%) and times of spraying of this nano particle (vegetative and reproductive stages) were applied. Traits of height, 1000 grain weight, grain yield, essential oil percentage and essential oil yield, were analysed using the SAS software. Results showed that the effect of concentrations of titanium dioxide nanoparticle was significant on all traits with the exception of essential oil percentage trati. But the effect of times of spraying of this nano particle, was significant only on trait of height. So that the highest amount of height, was obtained at vegetative stage. Also according to the results, concentration of 0.06% nano-TiO2, in comparison with the other examined concentrations of this nanoparticle and control or no application of it, was the most positive and effective treatment. Therefore, in this experiment, application of nano-TiO2, especially at concentration of 0.06%, was effective for gain the highest essential oil yield of cumin.